linux-kernel - Re: [PATCH] kallsyms: fix potential overflow in binary search

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Message-ID: <482AD08D.7070206@grupopie.com>
Date:	Wed, 14 May 2008 12:44:13 +0100
From:	Paulo Marques <pmarques@...popie.com>
To:	Vegard Nossum <vegard.nossum@...il.com>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kallsyms: fix potential overflow in binary search

Vegard Nossum wrote:
>>>From 61b840f071e496f632fcc293f5435428cfc98844 Mon Sep 17 00:00:00 2001
> From: Vegard Nossum <vegard.nossum@...il.com>
> Date: Tue, 13 May 2008 10:20:27 +0200
> Subject: [PATCH] kallsyms: fix potential overflow in binary search
> 
> This will probably never trigger... but it won't hurt to be careful.

Not "probably", this will never trigger _period_. If you ever have more 
than 2^31 symbols in the kernel's kallsyms table you'll have worse 
problems to worry about than the binary search overflowing.

So, I don't think it is worth this des-optimization at all...

> http://googleresearch.blogspot.com/2006/06/extra-extra-read-all-about-it-nearly.html
> 
> Signed-off-by: Vegard Nossum <vegard.nossum@...il.com>
> ---
>  kernel/kallsyms.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index 6fc0040..38fc10a 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -176,7 +176,7 @@ static unsigned long get_symbol_pos(unsigned long addr,
>  	high = kallsyms_num_syms;
>  
>  	while (high - low > 1) {
> -		mid = (low + high) / 2;
> +		mid = low + (high - low) / 2;
>  		if (kallsyms_addresses[mid] <= addr)
>  			low = mid;
>  		else


-- 
Paulo Marques - www.grupopie.com

Dear aunt, let's set so double the killer delete select all.
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